1. Field of the Invention
This invention relates to a safety pressure relief valve assembly having anti-blocking means associated with at least one of the open ends thereof for preventing foreign matter from entering the ends thereby keeping the safety pressure relief assembly in full operational condition at all times.
2. Prior Art Statement
A pressure relief valve as commonly utilized on the fill spout of an automobile fuel tank comprises a portion of the closure of the tank. This closure is generally further enclosed in a receptacle disposed in the fender of the automobile for protection from the elements. Such mountings are not, however, commonplace in railroad locomotives which have fuel tanks mounted from the lower portion of the frame extending from side to side of the locomotive. The locomotive fuel tank commonly has a solid closure for the end of the fuel spout and usually has a vent port disposed in the upper surface of the tank remote from the fuel spout. The fuel tank venting system then has a vent pipe associated with the vent port extending along the upper surface and one end of the tank. The terminal end of the vent pipe is open to the atmosphere and is often located just forward of one wheel of the locomotive. The terminal end of the vent pipe has a tendency to become blocked with an accumulation of ice and snow thrown against the end of the fuel tank and the vent pipe during periods of inclement weather. In other cases, a safety pressure valve having an open discharge end is mounted on the vent port on the top surface of the tank remote from the fuel spout. Pressure relief valves for locomotives are generally tubular having a body defined by at least one upstanding peripheral wall and having open ends, means associated with one end of the body for attaching to a fuel tank, a bore through the body, a valve seat disposed in an internal flange in the bore and a valve member resting on the seat, the valve member having a biasing means associated therewith for biasing the valve member against the valve seat in a direction toward the one end. Such a valve is part number 3397E manufactured by Clayton Mark, Inc. of Rogers, Ark. This valve has an open end which is generally upwardly disposed and is subject to accumulation of foreign matter in the open end thereof which may block the proper operation of the valve. For instance, ice formed from rain or the melting of snow and subsequent freezing thereof is a common failure of these pressure relief valves and when the locomotive is fueled, splash back occurs when the nozzle is removed from the tank as the tank has become pressurized. This safety hazard may result in fire but always results in spillage of fuel into the environment. Therefore, there exists a need for a safety pressure relief assembly having a means on the discharge end thereof for preventing foreign matter from entering the discharge end thereby keeping the safety pressure relief assembly in full operational condition at all times.
Locomotive fuel tanks also usually have a tank level indicator comprising a float attached to the end of an elongated arm pivotally mounted in an indicating device. The vibration of the locomotive engine and the movement of the fuel in the tank often causes the float to become separated from the elongated arm. The float migrates toward the pressure vent port as the air above the fuel is vented during the fueling operation. The float becomes lodged in the end of the vent port causing pressure to build up in the fuel tank during fueling operations creating a hazardous material spill into the environment. Therefore, there also exists a need for a safety pressure relief assembly having a means associated with the inlet end thereof for preventing the inclusion of foreign matter in the inlet end thereby keeping the safety pressure relief assembly in full operational condition at all times. There is also a need to have a fuel tank venting system having means associated with the vent port for preventing the inclusion of foreign matter in the tank from blocking the vent port thereby allowing full functionality of a safety pressure relief valve assembly disposed elsewhere in the venting system.
It is known to provide a pressure relief valve for tankers for oil products and chemicals having an upwardly facing blow-off opening with a valve and valve seat in the opening from which ice may be manually removed. For instance, see the U.S. Pat. No. 5,060,688 issued on Oct. 29, 1991 to Emil Sorensen.
It is also known to provide a safety pressure-vacuum relief assembly for remote mounting on a vehicle fuel tank comprising a tubular fitting having an flared upper end with a plurality of venting holes in a flat plastic plate resting on a substantially flat flange circumscribing the upper end with an inverted cup having a peripheral skirt encompassing the plastic plate and the flange, the inverted cup having ports in a floor thereof and the assembly having a shield with a down turned peripheral skirt axially spaced from the cup floor. For instance, see the U.S. Pat. No. 3,929,158 issued on Dec. 30, 1975 to Robert E. Rogers.
Finally, it is known to provide a fluid flow-controlling valve comprising a valve body, a valve seat extending around a bore in the body, a relief valve element coaxial with and arranged for axial displacement within the bore and a cap coaxial with the bore wherein the cap has a radial bore intercepting a bore in the upper end of the cap providing the safety VIP relief outlet. For instance, see the U.S. Pat. No. 3,976,096 issued on Aug. 24, 1976 to Gerald H. Kass.